A communication system is formed, at a minimum, by a transmitter and a receiver interconnected by a communication channel. Communication signals generated by the transmitter are transmitted upon the communication channel to be received by the receiver.
A radio communication system is a communication system in which the communication channel is formed of a portion of the electromagnetic frequency spectrum. Because a fixed or hard-wired connection is not required to be formed between the transmitter and the receiver, a radio communication system is advantageously utilized when the use of such fixed or hard-wired connections would be inconvenient or impractical.
A communication system, sometimes generically referred to as a "cellular" communication system is exemplary of a radio communication system. When the infrastructure, also referred to as the network, of a cellular communication system is installed throughout a geographical area, a subscriber, positioned at any location throughout the area encompassed by the system, is able to communicate by way of the system with a mobile terminal.
The network of one exemplary cellular communication system is formed of spaced-apart, fixed-site base stations which include transceivers. In such exemplary system each fixed-site, base station defines a "cell." As the mobile terminal used by the subscriber to communicate with another communication station travels between cells, uninterrupted communication is possible by "handing-over" communications from one base station to another.
Several analogous types of wireless communication systems have been implemented, and others have been proposed, to encompass limited areas, such as the area encompassed by a building structure or office workplace. Because the areas intended to be encompassed by such systems are typically fairly small, the networks of such systems are sometimes referred to as microcellular networks. Such networks are sometimes also referred as indoor networks. And, because such networks are also sometimes permitted to be used only by selected groups, such as employees of a business in which the networks are installed, the networks are sometimes also referred to as private networks. While the description herein utilizes such terminology, it should be understood that such networks need not be installed only in indoor areas or that such networks define cells of only small areas.
Networks, typically having a large number of fixed-site transceivers spaced-apart over a large area, in contrast, are sometimes referred to as macrocellular or outdoor networks. Also, such networks are sometimes also referred to as being public networks as subscriptions for service pursuant to such networks are typically available to the general public. While such terminology is also used herein, it should also be understood that such networks need not be installed only to encompass outdoor areas, define cells of only large areas, or be public in nature. Such networks might well include cells of both large and small areas and cells intended to encompass only indoor areas as well as cells intended to encompass outdoor areas. A communication system might be formed to include both a macrocellular network and a microcellular network, each network forming a portion of the infrastructure of the communication system. The terms macrocellular network portion and microcellular network portion shall be used below to indicate that such networks may form portions of the communication system.
Mobile terminals have been constructed in which communications are permitted therethrough with both the macrocellular communication network portion and a microcellular communication network portion. When the mobile terminal is positioned within an area intended to be encompassed by a microcellular network portion, communication with the microcellular network portion can be effectuated. And, when the mobile terminal is positioned at a location encompassed by a macrocellular communication network portion, communication can be effectuated between the mobile terminal and the macrocellular network portion.
Costs associated with communicating by way of a microcellular network portion are sometimes less than corresponding costs associated with communicating by way of a macrocellular network. Also, higher levels of services, e.g., additional service subscriptions for premium service features, might be available in the microcellular network portion but not in the macrocellular network portion. Also, security levels might be higher in the microcellular network portion, e.g., the microcellular network portion might be a proprietary network. Therefore, when a mobile terminal is positioned within an area intended to be encompassed by the microcellular cellular network portion, it is generally desirable that communications utilizing the mobile terminal be effectuated by way of the microcellular network portion.
Mobile terminals operable in a communication system having both a microcellular network portion and a macrocellular network portion are sometimes able to make signal strength, or other signal quality, measurements of control signals generated by fixed-site transceivers of the networks. Based upon such signal strength, or other signal quality, measurements, decisions are made as through with which fixed-site transceiver the mobile terminal should communicate. Such decisions might also be determinative of through which of the network portions the mobile terminal communicates. Hand-over requests of ongoing communications are also made based upon such measurements.
In a communication system in which the mobile terminals do not make such measurements, analogous measurements are made by the communication system infrastructure.
Measurements, either those made by a mobile terminal or those made at the infrastructure, are made when the mobile terminal is in the active mode, i.e., when the mobile terminal is being used in on-going communications.
Measurements might also be made when the mobile terminal is in the idle mode, i.e., when the mobile terminal is turned-on, but not used in ongoing communications.
As mentioned above, it is usually desirable for a mobile terminal to communicate with another communication station by way of a microcellular network portion when the mobile terminal is positioned in an area intended to be encompassed by the microcellular network portion. Actual coverage areas of the macrocellular and microcellular network portions might, however, overlap.
That is, even though the network portions are constructed such that the microcellular network portion is intended to encompass a particular, defined area, the actual coverage areas encompassed by the different network portions might overlap. Because of such overlap, a handover may be possible from a coverage point of view and a mobile terminal might be instructed to communicate by way of a fixed-site transceiver of one network portion when positioned at a location intended to be encompassed by the other network portion.
For instance, when a microcellular network forming a portion of a communication system is constructed within a building, communication by a mobile terminal with another communication station, when positioned within the building, would generally be desired to be effectuated with the microcellular network portion. Only when the mobile terminal exits the building should handover of communications by way of the macrocellular network portion be permitted. However, when the coverage areas of the network portions overlap, measurements by the mobile terminal might indicate that the mobile terminal should be communicating by way of one of the network portions when positioned at a location intended to be encompassed by the other network portion.
When, for example, the mobile terminal is positioned close to a window or other exterior portion of the building in which the microcellular network portion is installed, measurements taken by the mobile terminal might indicate that the mobile terminal should be communicating by way of a fixed-site transceiver of the macrocellular network portion rather than the microcellular network portion. When communications are ongoing when such a measurement is made, an attempt to hand-over the ongoing communications from the microcellular network portion to the macrocellular network portion might be made. If permitted, the advantages associated with communicating by way of the microcellular network portion would be obviated.
A manner by which better to control through which of the network portions the mobile terminal is permitted to communicate with another communication station would therefore be advantageous.
It is in light of this background information related to communications in a wireless communication system having at least two network portions, such as a macrocellular network portion and a microcellular network portion, that the significant improvements of the present invention have evolved.